Eccentric oscillating gear device and assembling method for crankshaft in eccentric oscillating gear device

ABSTRACT

An eccentric oscillating gear device comprises a crankshaft having an eccentric portion, an externally toothed gear having external teeth and a through-hole in which the eccentric portion is inserted, an outer cylinder, and a carrier. The carrier rotatably supports the crankshaft. The outer cylinder has internal teeth meshed with the external teeth of the externally toothed gear. The eccentric oscillating gear device is provided with rotational phase adjusting section for setting an orientation of the crankshaft about an axis thereof, on the basis of orientations of the outer cylinder and the carrier about an axis thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an eccentric oscillating gear device,and a method of assembling a crankshaft in the eccentric oscillatinggear device.

2. Description of the Related Art

Heretofore, there has been known an eccentric oscillating gear devicedisclosed in JP 2001-353684A. The eccentric oscillating gear devicedisclosed in JP 2001-353684A is designed such that an externally toothedgear is oscillatingly rotated interlockingly with a rotation of aneccentric body provided on a crankshaft, to allow an outer cylinder anda carrier to be relatively rotated with respect to each other. In thisgear device, the outer cylinder is fixed to a first member of a robot,and the carrier is adapted to be relatively rotated at a given rotationratio with respect to the outer cylinder, and fixed to a second memberof the robot. This gear device is provided with a positioning pin forsetting the carrier to a given orientation with respect to the secondmember of the robot.

Meanwhile, in an operation of assembling an eccentric oscillating geardevice, generally, a crankshaft and an externally toothed gear areassembled to a carrier, and then the carrier is assembled to an outercylinder. In this case, the crankshaft can be assembled to the carrierwithout any restriction in terms of an eccentric direction of aneccentric body of the crankshaft. However, depending on the eccentricdirection of the assembled crankshaft, a rotational phase differenceoccurs in torsional rigidity of the gear device. This causes a problemthat, in cases where the gear device is disassembled during maintenanceor the like and then re-assembled, a phase of the torsional rigidity ina rotation direction is changed from that before the disassembling.Moreover, the gear device is free from restriction in terms of theeccentric direction. Thus, there is another problem that an individualdifference in phase of the torsional rigidity in the rotation directionoccurs between respective ones of a plurality of the gear devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an eccentricoscillating gear device capable of solving the above problems, and amethod of assembling a crankshaft in the eccentric oscillating geardevice.

More specifically, the present invention is directed to reducing avariation in phase of torsional rigidity of an eccentric oscillatinggear device in a rotation direction.

According to one aspect of the present invention, there is provided aneccentric oscillating gear device for transmitting driving force whilechanging a rotation speed at a given rotation speed ratio between afirst member and a second member. The gear device comprises a crankshafthaving an eccentric portion, a gear member having a tooth portion and athrough-hole in which the eccentric portion is inserted, a firstcylindrical section adapted to be attachable to one of the first andsecond members, and a second cylindrical section adapted to beattachable to a remaining one of the first and second members. One ofthe first and second cylindrical sections rotatably supports thecrankshaft, and a remaining one of the first and second cylindricalsections has a tooth portion meshed with the tooth portion of the gearmember. The first and second cylindrical sections are adapted to berotatable concentrically and relatively with respect to each otheraccording to an oscillating movement of the gear member along with arotation of the crankshaft. The eccentric oscillating gear device isprovided with rotational phase adjusting section for setting anorientation of the crankshaft about an axis thereof, on the basis oforientations of the first and second cylindrical sections about an axisthereof.

According to another aspect of the present invention, there is provideda method of assembling a crankshaft in an eccentric oscillating geardevice for transmitting driving force while changing a rotation speed ata given rotation speed ratio between a first member and a second member.The crankshaft assembling method comprises the steps of: assembling acrankshaft having an eccentric portion to a gear member; assembling thecrankshaft to one of a first cylindrical section and a secondcylindrical section; assembling the gear member to a remaining one ofthe first and second members which has a tooth portion; and combiningthe first and second cylindrical sections together. In the crankshaftassembling method, the step of assembling the crankshaft to one of afirst cylindrical section and a second cylindrical section includesusing rotational phase adjusting section to set an orientation of thecrankshaft about an axis thereof, with respect to one of the first andsecond cylindrical sections, and the step of combining the first andsecond cylindrical sections together includes using the rotational phaseadjusting section to set an orientation of the second cylindricalsection about an axis thereof, with respect to the first cylindricalsection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an eccentric oscillating gear deviceaccording to one embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG. 1.

FIG. 3 is a view from the line III-III in FIG. 1.

FIG. 4 is a perspective view of a temporary locking pin.

FIGS. 5A to 5D are diagrams illustrating a rotational phase.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, the present invention will now bespecifically described based on one embodiment thereof.

As illustrated in FIG. 1, an eccentric oscillating gear device 10according to this embodiment comprises: an outer cylinder 12 serving asa first cylindrical section; a carrier 14 disposed inside the outercylinder 12 to serve as a second cylindrical section adapted to berelatively rotatable with respect to the outer cylinder 12; an inputshaft 16 adapted to generate a rotational driving force for rotating thecarrier 14; and a speed reduction mechanism 18 adapted to rotate thecarrier 14 at a rotation speed reduced at a given ratio with respect toa rotation speed of the input shaft 16. The gear device 10 is designedto transmit driving force while changing a rotation speed at a givenrotation speed ratio, between a first arm 20 serving as a first member,and a second arm 38 serving as a second member. For example, the geardevice 10 is configured as a speed reducer for use in an articulatedjoint for robot arms.

The outer cylinder 12 is formed in a cylindrical shape, and an innerperipheral surface of the outer cylinder 12 has a large number of pingrooves 12 c formed at even intervals in a circumferential directionthereof. As also illustrated in FIG. 2, a pin-shaped internal tooth 24is fitted in each of the pin grooves 12 c. In other words, in thisembodiment, the outer cylinder 12 serving as the first cylindricalsection has internal teeth 24.

The outer cylinder 12 has an outer peripheral portion integrallyprovided with a flange 12 a. The flange 12 a has a plurality ofbolt-insertion holes 12 b provided at even intervals in acircumferential direction thereof. In this embodiment, thebolt-insertion hole 12 b is provided in a number of eight. The outercylinder 12 and the first arm 20 are fastened together by inserting aplurality of bolts 21 in respective ones of the bolt-insertion holes 12b, and screwing the inserted bolts 21 with respective ones of aplurality of screw holes 20 c of the first arm 20. One of axiallyopposite ends (in FIG. 1, a right end) of the outer cylinder 12 isclosed by the first arm 20. A motor 22 serving as a driving source isfixed to the first arm 20 which has a drive-shaft insertion hole 20 aformed to penetrate therethrough in a thickness direction thereof so asto allow a drive shaft 22 a of the motor 22 to be inserted thereinto.

The carrier 14 is supported by the outer cylinder 12 through a pair ofmain bearings 26 disposed in axially spaced-apart relation. Thus, thecarrier 14 is adapted to be rotatable concentrically with the outercylinder 12. In other words, the carrier 14 is adapted to be rotatedabout an axis O1 of the outer cylinder 12 and relatively with respect tothe outer cylinder 12. Each of the main bearings 26 is composed of anangular ball bearing.

The carrier 14 comprises a circular disk-shaped end plate portion 30serving as a first side portion, a circular disk-shaped base plateportion 32 serving as a second side portion, and a shaft portion 33protrudingly provided on one surface of the base plate portion 32. Theshaft portion 33 is integrally formed with the base plate portion 32. Asillustrated in FIG. 2, the shaft portion 33 has a generally hexagonalshape in cross-section. In this embodiment, the shaft portion 33 isprovided in a number of three, wherein the three shaft portions 33 arearranged at even intervals in a circumferential direction of the baseplate portion 32. After a distal end face of the shaft portion 33 isbrought into contact with the end plate portion 30, the shaft portion 33is fastened to the end plate portion 30 by a bolt 34. In this state, aspace having a given width in the axial direction is defined between thebase plate portion 32 and the end plate portion 30.

The shaft portion 33 is provided with a bolt-fastening hole 33 a. Thebolt 34 is inserted into a bolt-insertion hole 30 a of the end plateportion 30 from a side opposite to the shaft portion 33, and screwedwith the bolt-fastening hole 33 a of the shaft portion 33. Further, apin 36 is provided to extend between the shaft portion 33 and the endplate portion 30 so as to position the end plate portion 30 with respectto the base plate portion 32. Instead of being integrally formed withthe base plate portion 32, the shaft portions 33 may be integrallyformed with the end plate portion 30. In this case, the shaft portions33 will be fastened to the base end portion 32.

The base end portion 32 is attached to the second arm 38 as acounterpart member, through an end face 32 c thereof on a side oppositeto the end plate portion 30. The second arm 38 is formed with aplurality of bolt-insertion holes 38 a, and the base plate portion 32has a plurality of fastening holes 32 d formed at positionscorresponding to respective ones of the bolt-insertion holes 38 a. Thesecond arm 38 and the base plate portion 32 are fastened together byinserting a plurality of bolts 37 in respective ones of thebolt-insertion holes 38 a of the second arm 38, and screwing theinserted bolts 37 with respective ones of the fastening holes 32 d ofthe base plate portion 32. Two or more (five) of the fastening holes 32d are disposed at even intervals to form a fastening-hole group. Thefastening-hole group is provided in a number of three, wherein the threefastening-hole groups are disposed about the axis O1 at even intervals(see FIG. 3).

As illustrated in FIG. 1, the end plate portion 30 and the base plateportion 32 are formed, respectively, with a through-hole 30 b and athrough-hole 32 a each penetrating through a central region thereof inthe axial direction. Each of the through-holes 30 b, 32 a is adapted toallow the input shaft 16 to be inserted thereinto. The input shaft 16 isinserted in the through-holes 30 b, 32 a and disposed coaxially with theouter cylinder 12.

The input shaft 16 has a base end coaxially joined to the drive shaft 22a of the motor 22, and a distal end located within the through-hole 32 aof the base plate portion 32. The distal end of the input shaft 16 isintegrally provided with a drive gear 42 composed of an externallytoothed gear.

The speed reduction mechanism 18 comprises spur gears 44, crankshafts46, and externally toothed gears (a first externally toothed gear 48 aand a second externally toothed gear 48 b) serving as gear members. Eachof the first and second externally toothed gears 48 a, 48 b has externalteeth meshed with the internal teeth of the outer cylinder 12. The spurgear 44 is splined to a base plate portion-side end of the crankshaft46, and meshed with the drive gear 42 provided on the input shaft 16.Thus, driving force is transmitted to the crankshaft 46 through the spurgear 44, so that the crankshaft 46 is interlocked with a rotation of theinput shaft 16.

The crankshaft 46 is disposed parallel to the input shaft 16. Thecrankshaft 46 is rotatably supported by the end plate portion 30 througha first crankshaft bearing 51, and rotatably supported by the base plateportion 32 through a second crankshaft bearing 52. In other words, thefirst crankshaft bearing 51 is disposed between the end plate portion 30and the crankshaft 46, and the second crankshaft bearing 52 is disposedbetween the base plate portion 32 and the crankshaft 46. Each of thefirst and second crankshaft bearings 51, 52 is composed of a taperedroller bearing.

The end plate portion 30 and the base plate portion 32 are formed with athrough-hole 30 c and a through-hole 32 b, respectively. Thethrough-hole 30 c (32 b) is formed in a number of three, wherein thethree through-holes 32 c (32 b) are arranged around the through-hole 30b (32 a) at even intervals in a circumferential direction. Thecrankshaft 46 is provided in a number of three, wherein the threecrankshafts 46 are disposed at even intervals in the circumferentialdirection (see FIG. 2), while penetrating through respective paired onesof the through-holes 30 c, 32 b.

The crankshaft 46 has a shaft body 46 c, and eccentric portions (a firsteccentric portion 46 a and a second eccentric portion 46 b) integrallyformed on the shaft body 46 c. The shaft body 46 c has across-sectionally circular shape, and each of the first and secondeccentric portions 46 a, 46 b is eccentrically disposed with respect toa crankshaft axis O2 which is an axis of the shaft body 46 c. The firstand second eccentric portions 46 a, 46 b are shifted in phase angle withrespect to each other. Specifically, an eccentric direction of the firsteccentric portion 46 a with respect to the crankshaft axis O2 and aneccentric direction of the second eccentric portion 46 b with respect tothe crankshaft axis O2 are different from each other, and the respectivephase angles of the first and second eccentric portions 46 a, 46 b areshifted in phase angle by 180 degrees. The three crankshafts 46 areassembled to allow respective eccentric directions of the firsteccentric portions 46 a thereof to coincide with each other.

The first and second eccentric portions 46 a, 46 b are disposed betweenthe first and second crankshaft bearings 51, 52 in axially adjacentrelation to each other. The first eccentric portion 46 a is disposedadjacent to the first crankshaft bearing 51, and the second eccentricportion 46 b is disposed adjacent to the second crankshaft bearing 52.

Each of the first externally toothed gear 48 a and the second externallytoothed gear 48 b is disposed within the space between the base plateportion 32 and the end plate portion 30. As also illustrated in FIG. 2,each of the first and second externally toothed gears 48 a, 48 b isformed with a first through-hole 48 c for allowing the input shaft 16 topenetrate therethrough, a second through-hole 48 d for allowing each ofthe shaft portions 33 to penetrate therethrough, and a thirdthrough-hole 48 e for allowing the first and second eccentric portions46 a, 46 b of each of the crankshafts 46 to penetrate therethrough.

A roller bearing 55 is attached to each of the first and secondeccentric portions 46 a, 46 b. In this state, the first eccentricportion 46 a is inserted in the third through-hole 48 e of the firstexternally toothed gear 48 a, and the second eccentric portion 46 b isinserted in the third through-hole 48 e of the second externally toothedgear 48 b. According to oscillating movements of the first and secondeccentric portions 46 a, 46 b along with a rotation of the crankshaft46, the first and second externally toothed gears 48 b are rotated whilebeing meshed with the internal teeth 24 of the outer cylinder 12. Inthis embodiment, the gear device is designed such that the externallytoothed gear is provided in a number of two. Alternatively, the geardevice may be designed such that the externally toothed gear is providedin a number of one or in a number of three or more.

As illustrated in FIGS. 1 and 3, the through-hole 32 a and the threethrough-holes 32 b of the base plate portion 32 are communicated witheach other, i.e., formed as a single through-hole, in the end face 32 con the side opposite to the end plate portion 30. The spur gear 44 islocated within the single through-hole at a position corresponding toeach of the through-holes 32 b. Thus, when the base plate portion 32 isdetached from the second arm 38, one principal surface 44 a of the spurgear 44 is exposed.

As illustrated in FIG. 3, the eccentric oscillating gear device 10 isprovided with rotational phase adjusting means 58 for setting anorientation of the crankshaft 46 about the axis thereof, on the basis oforientations of the outer cylinder 12 and the carrier 14 about the axisthereof. The rotational phase adjusting means 58 comprises a firstreference portion 58 a, a second reference portion 58 b and a thirdreference portion 58 c.

The first reference portion 58 a is provided in the outer cylinder 12 ata given position offset from the axis O1. In this embodiment, the firstreference portion 58 a is composed of a hole formed in the flange 12 aof the outer cylinder 12. The first reference portion 58 a is providedin a number of one, wherein the one first reference portion 58 a isformed at a position to be aligned with a pin hole 20 b (see FIG. 1) ofthe first arm 20 when the flange 12 a is fastened to the first arm 20.

As mentioned above, the plurality of bolt-insertion holes 12 b areformed in the flange 12 a at even intervals in the circumferentialdirection of the flange 12 a. Thus, as long as each of thebolt-insertion holes 12 b is alignable with a respective one of thescrew holes 20 c of the first arms 20, a circumferential orientation ofthe outer cylinder 12 can be variously set with respect to the first arm20. However, based on providing the first reference portion 58 a, anorientation of the outer cylinder 12 about the axis O1 is fixed.Specifically, when the first reference portion 58 a is aligned with thepin hole 20 b formed in the first arm 20, the orientation of the outercylinder 12 about the axis thereof is set to a given state with respectto the first arm 20. In this state, the outer cylinder 12 is fixedlyattached to the first arm 20. Further, respective circumferentialpositions of the pin grooves 12 c with respect to the first arm 20 arealso set.

A pin (position adjustment member) 60 (see FIG. 1) may be inserted toextend between the first reference portion 58 a and the pin hole 20 b ofthe first arm 20 so as to reliably perform the position adjustment.After completion of the position adjustment, the pin 60 may be detached.

Alternatively, the bolt-insertion holes 12 b formed in the flange 12 ain the circumferential direction thereof may be intentionally arrangedat uneven intervals so as to allow the circumferential orientation ofthe outer cylinder 12 with respect to the first arm 20 to be set only ina single way. In this case, the bolt-insertion holes 12 b arranged atuneven intervals are used as the first reference portion 58 a.

The second reference portion 58 b is provided in the carrier 14 at agiven position offset from the axis O1. In this embodiment, the secondreference portion 58 b is composed of a hole formed in the end face 32 cof the base plate portion 32 of the carrier 14 on the side of the spurgears 44. More specifically, the second reference portion 58 b isprovided in the end face 32 c of the base plate portion 32 which facesthe second arm 38. The second reference portion 58 b is provided in anumber of one, wherein the one second reference portion 58 b is formedat a position to be aligned with a pin hole 38 b (see FIG. 1) of thesecond arm 38 when the base plate portion 32 of the carrier 14 isfastened to the second arm 38.

As mentioned above, the plurality of fastening holes 32 d are formed inthe base plate portions 32 in the circumferential direction thereof.Thus, as long as each of the fastening holes 32 d is alignable with arespective one of the bolt-insertion hole 38 a of the second arms 38, acircumferential orientation of the base plate portion 32 (carrier 14)can be variously set with respect to the second arm 38. However, basedon providing the second reference portion 58 b, an orientation of thebase plate portion 32 (carrier 14) about the axis thereof is specified.

When the second reference portion 58 b is aligned with the pin hole 38 bformed in the second arm 38, the orientation of the carrier 14 about theaxis thereof is set to a given state with respect to the second arm 38.In this state, the carrier 14 is fixedly attached to the second arm 38.A temporary locking pin 62 (see FIGS. 3 and 4) may be inserted to extendbetween the second reference portion 58 b and the pin hole 38 b of thesecond arm 38 so as to reliably perform the position adjustment. Afterthe position adjustment is completed by fixedly attaching the carrier 14to the second arm 38, the temporary locking pin 62 may be detached.

Alternatively, the fastening holes 32 d formed in the base plate portion32 in the circumferential direction thereof may be arranged in aspecific pattern so as to allow the circumferential orientation of thebase plate portion 32 (carrier 14) with respect to the second arm 38 tobe set only in a single way. In this case, the fastening holes 32 dformed in the base plate portion 32 are used as the second referenceportion 58 b.

The temporary locking pin 62 is formed as a three-forked pin whichcomprises a pin body 62 a formed in an arc shape, legs 62 b eachextending from a respective one of opposite ends of the pin body 62 a,and a leg 62 c extending from an intermediate portion of the pin body 62a. The leg 62 c extending from the intermediate portion is adapted to beinsertable into the pin hole 38 b of the second arm 38 and the secondreference portion 58 b of the carrier 14.

The third reference portion 58 c is provided in the spur gear 44 at agiven position offset from the crankshaft axis O2. The third referenceportion 58 c is provided in each of the three spur gears 44, whereineach of the third reference portions 58 c is set at a position where ithas a given directional relation with the eccentric directions of thefirst and second eccentric portions 46 a, 46 b with respect to thecrankshaft axis O2 of the crankshaft 46. In other words, each of thethird reference portions 58 c has the same positional relationship witha corresponding one of the crankshaft axes O2. For example, the thirdreference portion 58 c may be formed in a direction coinciding with theeccentric direction of the second eccentric portion 46 b. Alternatively,as long as a positional relationship with each of the first and secondeccentric portions 46 a, 46 b can be known, the third reference portion58 c may be formed at any position.

The third reference portion 58 c is composed of a hole formed in theprincipal surface 44 a of the spur gear 44. The principal surface 44 ais exposed when the second arm 38 is detached. Specifically, the thirdreference portion 58 c is provided in the surface 44 a facing the secondarm 38, as with the second reference portion 58 b provided in the endface 32 c of the base plate portion 32 of the carrier 14. One of thethird reference portions 58 c is provided in a respective one of thespur gears 44. Each of the legs 62 b at the ends of the temporarylocking pin 62 is adapted to be insertable into the third referenceportion 58 c under a condition that the middle leg 62 c of the temporarylocking pin 62 is inserted into the second reference portion 58 b of thecarrier 14 as mentioned above.

The temporary locking pin 62 is not limited to the three-forked type.For example, a two-forked temporary locking pin 62 formed by omittingone of the end legs 62 b may be employed. In this case, one 62 c of twolegs of the temporary locking pin 62 is inserted into the secondreference portion 58 b, and the other leg 62 b is inserted into thethird reference portion 58 c. Further, in this case, an additionaltemporary locking pin (illustration is omitted) may be used to, afterpositioning one of the three spur gears 44 (or crankshaft 46) withrespect to the carrier 14, position the remaining two spur gears 44 (ortwo crankshafts 46) with respect to the positioned spur gear 44. In thiscase, the additional temporary locking pin may have a pin body 62 aformed in a triangular shape to allow three legs thereof to besimultaneously inserted into respective ones of the third referenceportions 58 c.

Alternatively, a temporary locking pin (illustration is omitted) forpositioning the second reference portion 58 b with respect to the secondarm 38, and a temporary locking pin (illustration is omitted) forpositioning the spur gear 44 (crankshaft 46) with respect to the carrier14, may be formed as separate pins. In this case, the temporary lockingpin for positioning the carrier 14 with respect to the second arm 38 maybe composed of a rod-like pin. This rod-like pin may be used withoutbeing detached.

An operation of the eccentric oscillating gear device 10 according tothis embodiment will be briefly described below. In the gear device 10,the input shaft 16 is driven by driving force of the motor 22, and,according to a resulting rotation of the input shaft 16, the spur gears44 are rotated through the drive gear 42. Thus, each of the crankshafts46 is rotated together with a corresponding one of the spur gears 44.Upon rotation of the crankshaft 46, according to an oscillating movementof the first eccentric portion 46 a, the first externally toothed gear48 a is rotated while being meshed with the internal teeth 24. Further,according to an oscillating movement of the second eccentric portion 46b, the second externally toothed gear 48 b is rotated while being meshedwith the internal teeth 24. Thus, the carrier 14 having the shaftportions 33 each penetrating through the second through-holes 48 d ofthe first and second externally toothed gears 48 a, 48 b is rotated.Thus, the second arm 38 is relatively rotated with respect to the firstarm 20. A rotation speed of the second arm 38 (carrier 14) has a valuewhich is reduced at a given ratio with respect to a rotation speed inputinto the input shaft 16.

A reason for adjusting a rotational phase of the crankshaft 46 withrespect to the outer cylinder 12 and the carrier 14 will be describedbelow. FIG. 5A is a schematic diagram illustrating a positionalrelationship between respective ones of the first reference portion 58 arepresenting a reference point of the outer cylinder 12, the secondreference portion 58 b representing a reference point of the carrier 14,and the third reference portion 58 c representing a reference point ofthe crankshaft 46. FIG. 5B schematically illustrates a position of thefirst reference portion 58 a on the first arm 20, and a position of thesecond reference portion 58 b on the second arm 38. FIGS. 5A and 5Billustrate a state when the outer cylinder 12, the carrier 14, and eachof the crankshafts 46, are set to a given orientation about the axis O1with respect to the first arm 20, a given orientation about the axis O1with respect to the second arm 38, and a given orientation about thecrankshaft axis O2, respectively. The solid line illustrated in FIG. 5Cindicates torsional rigidity in a rotation direction when the carrier 14in the above state is rotated about the axis O1 relatively with respectto the outer cylinder 12. The torsional rigidity is periodicallychanged. This is caused, for example, by a difference in circumferentialweight of the carrier 14 about the axis O1 (e.g., a difference in weightbetween portions with and without the through-holes 30 c, 32 b), and adifference in weight of the crankshaft 46 about the crankshaft axis O2.

FIG. 5D illustrates a state when the second reference portion 58 b isdisplaced about the axis O1 from the position illustrated in FIG. 5A byabout 30 degrees, and the third reference portion 58 c is rotated aboutthe crankshaft axis O2 with respect to the carrier 14. For example, FIG.5D may be assumed to be in a state when the gear device assembled asillustrated in FIG. 5A is disassembled for maintenance or the like andthen re-assembled.

The solid line in FIG. 5C indicates torsional rigidity occurring whenthe carrier 14 is rotated from the position illustrated in FIG. 5A, andthe broken line in FIG. 5C indicates torsional rigidity occurring whenthe carrier 14 is rotated from the position illustrated in FIG. 5D. Asis clear from FIG. 5C, the torsional rigidity becomes different betweenwhen an initial setting is performed in a coupled state between thefirst and second arms 20, 38 illustrated in FIG. 5A and when the initialsetting is performed in a coupled state between the first and secondarms 20, 38 illustrated in FIG. 5D, even if the second arm 38 is locatedat the same position with respect to the first arm 20. Thus, if arotational position adjustment between respective ones of the fivecomponents: the first arm 20, the second arm 38, the outer cylinder 12,the carrier 14 and the crankshaft 46, is not performed, the torsionalrigidity at an initial set position is changed, so that it is necessaryto perform a fine adjustment by means of teaching. Therefore, therotational phase adjustment between respective ones of the fivecomponents can be performed to reduce a variation in torsional rigidity.In the above description, the reason for a variation in torsionalrigidity has been explained by taking a variation in orientation of thecarrier 14 with respect to the outer cylinder 12 as an example. However,the variation in torsional rigidity is also caused by a difference inorientation (eccentric direction) of the crankshaft 46 with respect tothe outer cylinder 12, and by a difference in orientation (eccentricdirection) of the crankshaft 46 with respect to the carrier 14. Thus, itis necessary to adjust orientations between respective ones of the outercylinder 12, the carrier 14 and the crankshaft 46.

A process of assembling the crankshaft 46 in the eccentric oscillatinggear device 10 will be briefly described below. In the process ofassembling the crankshaft 46, the crankshaft 46 provided with the firstand second eccentric portions 46 a, 46 b and integrated with the spurgear 44 is first assembled to the carrier 14. In this assembling step,the temporary locking pin 62 is inserted into the second referenceportion 58 b and the third reference portion 58 c to set an orientationof the crankshaft 46 about the axis thereof with respect to the carrier14. In conjunction with the setting of the orientation of the crankshaft46 with respect to the carrier 14, the carrier 14 may be positioned withrespect to the second arm 38. Alternatively, the carrier 14 may besubsequently positioned with respect to the second arm 38.

Then, the carrier 14 is assembled to the outer cylinder 12. In thisassembling step, the first reference portion 58 a and the secondreference portion 58 b are used to set an orientation of the carrier 14about the axis thereof with respect to the outer cylinder 12. In thiscase, a positional relationship between the first reference portion 58 aand the second reference portion 58 b may be set to a given state on avisual basis, or using a two-forked temporary locking pin. Thus, anorientation of the crankshaft 46 about the crankshaft axis O2 is set onthe basis of the orientations of the outer cylinder 12 and the carrier14 about the axis O1. Then, the first arm 20 and the second arm 38 arefastened to the gear device using the pin 60 and the temporary lockingpin 62. This makes it possible to establish a coupled state between thefirst and second arms 20, 38 under a condition that the orientation ofthe outer cylinder 12 with respect to the first arm 20, the orientationof the carrier 14 with respect to the second arm 38, and the orientationof the crankshaft 46 with respect to the outer cylinder 12 and thecarrier 14, are set.

As described above, the eccentric oscillating gear device according tothe above embodiment is capable of setting an orientation of thecrankshaft 46 about the axis thereof, on the basis of orientations ofthe outer cylinder 12 and the carrier 14 about the axis thereof. Thus,when the outer cylinder 12 and the carrier 14 are attached,respectively, to the first arm 20 and the second arm 38, an orientationof the crankshaft 46 with respect to the first arm 20 and the second arm38 can be set through the orientations of the outer cylinder 12 and thecarrier 14. In other words, the orientation of the crankshaft 46 can beset using the rotational phase adjusting means. Thus, in cases where thegear device 10 is disassembled during maintenance or the like and thenre-assembled, it becomes possible to prevent a phase of torsionalrigidity in a rotation direction from being changed from that before thedisassembling. Further, it becomes possible to prevent an individualdifference in phase of the torsional rigidity in the rotation directionfrom occurring between respective ones of a plurality of the geardevices 10.

In the above embodiment, in an operation of assembling the crankshaft46, the crankshaft 46 is assembled to allow the third reference portion58 c to be set to a given position on the basis of the first referenceportion 58 a and the second reference portion 58 b. Thus, the crankshaft46 can be assembled such that an orientation thereof is set to a givenstate on the basis of the orientations of the outer cylinder 12 and thecarrier 14 about the axis thereof.

In the above embodiment, during assembling of the crankshaft 46, atwo-forked or three-forked temporary locking pin 62 is inserted toextend between the second reference portion 58 b and the third referenceportion 58 c each composed of a hole, so that it becomes possible toreliably set an orientation of the crankshaft 46 with respect to thecarrier 14. When the temporary locking pin 62 is subsequently detached,an eccentric oscillating gear device 10 can be provided in which thecrankshaft 46 is assembled to the carrier 14 under a condition that theorientation of the crankshaft 46 is adjusted to a given state.

The present invention is not limited to the above embodiment, butvarious changes and modifications may be made therein without departingfrom the spirits and scope of the present invention. For example,although the above embodiment has been described based on an examplewhere each of the first, second and third reference portions 58 a, 58 b,58 c is composed of a hole, the present invention is not limitedthereto. For example, at least one of the first, second and thirdreference portions 58 a, 58 b, 58 c may be composed of a markdiscriminable from its surroundings, based on color, convexity orconcavity.

Although the gear device according to the above embodiment is designedsuch that the third reference portion 58 c is provided in the spur gear44, the present invention is not limited thereto. For example, the thirdreference portion 58 c may be provided in any other suitable portionviewable from the side of the second arm 38, such as an end face of thecrankshaft 46 on the side of the second arm 38. Alternatively, the thirdreference portion 58 c may be provided in any other suitable portionviewable from the side of the first arm 20, such as an end face of thecrankshaft 46 on the side of the first arm 20.

The gear device according to the above embodiment is designed such thatthe spur gear 44 is joined to the end of the crankshaft 46.Alternatively, the spur gear 44 may be disposed between the firsteccentric portion 46 a and the second eccentric portion 46 b. In thiscase, the third reference portion 58 c may be provided in an end face ofthe crankshaft 46 or an end face of the second eccentric portion 46 b,as well as the one principal surface 44 a of the spur gear 44.

Although the gear device according to the above embodiment is designedsuch that the plurality of crankshafts 46 are arranged at positionsoffset from the axis O1 of the outer cylinder 12 at even intervals inthe circumferential direction, the present invention is not limitedthereto. For example, a so-called “center crank mechanism” may beemployed in which a single crankshaft 46 is disposed in concentricrelation with the outer cylinder 12 and the carrier 14. In this case,the third reference portion 58 c may be provided in a spur gear joinedto the crankshaft 46. Further, in a structure where a spur gear isomitted, the third reference portion 58 c may be formed in a distal endface of the crankshaft 46.

In the above embodiment, in an operation of adjusting a rotational phaseof the gear device 10, the temporary locking pin 62 is inserted into thesecond reference portion 58 b provided in the carrier 14, the thirdreference portion 58 c provided in the spur gear 44 and the pin hole 38b provided in the second arm 38 to adjust the rotational phase.Alternatively, the rotational phase of the gear device 10 may beadjusted before the assembling to the second arm 38. For example, thetemporary locking pin 62 is inserted into the second reference portion58 b and the third reference portion 58 c from the side of one end (inFIG. 1, a left end) of the gear device 10 to adjust rotational phases ofthe carrier 14 and the crankshaft 46. In this state, the gear device 10is assembled to the first arm 20 while adjusting the rotational phasethereof using the first reference portion 58 a. Then, the motor 22 isattached to the first arm 20 from the side of the other end (in FIG. 1,a right end) of the gear device 10, and the drive gear 42 of the inputshaft 16 is meshed with the spur gear 44. Then, the motor is powered onto allow a reference rotational phase to be recognized by a servo lockfunction, a brake attached to the motor or the like, and fixed. Then,the temporary locking pin is detached from the gear device. Even if thetemporary locking pin is detached, the carrier 14 and the crankshaft 46are kept from rotating, for example, by the servo lock function.Finally, the gear device 10 is attached to the second arm 38 whileadjusting respective positions of the second arm 38 and the first arm20.

Although the above embodiment has been described based on a structurecomprising the outer cylinder 12 provided with the internal teeth 24,and the first and second externally toothed gears 48 a, 48 b, thepresent invention is not limited thereto. For example, a structure maybe employed which comprises a carrier provided with external teeth, andan internally toothed gear. This type of gear device is disclosed, forexample, in JP 2000-065158A. Specifically, a carrier serving as thesecond cylindrical section is disposed coaxially with an outer cylinderserving as the first cylindrical section, while being partially locatedradially inward of the outer cylinder. The carrier has an outerperipheral surface provided with external teeth at a position radiallyinward of the outer cylinder. No tooth portion is provided on an innerperipheral surface of the outer cylinder. Further, a ring-shaped gearmember having an inner peripheral surface provided with internal teethmeshable with the external teeth of the carrier is disposed between thecarrier and the outer cylinder. The gear member is formed with athrough-hole for allowing an eccentric portion of a crankshaft to befitted therein. The crankshaft is rotated while receiving a torque froman input shaft directly or through a spur gear. The crankshaft iscircumferentially provided in a number of two or more, wherein each ofthe crankshafts is rotatably supported by the outer cylinder, and thegear member is adapted to be oscillated according to a rotation of thecrankshaft. Thus, the carrier having the external teeth meshed with theinternal teeth of the gear member is rotated. Further, a second armjoined to the carrier can be relatively rotated with respect to a firstarm joined to the outer cylinder. In this structure, the outer cylinderis formed with a first reference portion (e.g., a hole) for setting anorientation of the outer cylinder about an axis thereof with respect tothe first arm, and the carrier is formed with a second reference portion(e.g., a hole) for setting an orientation of the carrier about an axisthereof with respect to the second arm. Further, the crankshaft or thespur gear is formed with a third reference portion (e.g., a hole) forsetting an orientation of the crankshaft.

In the above embodiment, the outer cylinder is formed to serve as anexample of the first cylindrical section, and the carrier is formed toserve as an example of the second cylindrical section. Alternatively,the carrier may be formed to serve as an example of the firstcylindrical section, and the outer cylinder may be formed to serve as anexample of the second cylindrical section.

An outline of the above embodiment will be described below.

(1) The eccentric oscillating gear device according to the aboveembodiment is provided with rotational phase adjusting means for settingan orientation of the crankshaft about an axis thereof, on the basis oforientations of the first and second cylindrical sections about an axisthereof. This makes it possible to set the orientation of the crankshaftabout the axis thereof, on the basis of the orientations of the firstand second cylindrical sections about the axis thereof. Thus, when thefirst cylindrical section and the second cylindrical section areattached, respectively, to a first member and a second member, anorientation of the crankshaft with respect to the first member and thesecond member can be set through the orientations of the first andsecond cylindrical sections. Thus, in cases where the gear device isdisassembled during maintenance or the like and then re-assembled, itbecomes possible to prevent a phase of torsional rigidity in a rotationdirection from being changed from that before the disassembling.Further, it becomes possible to prevent an individual difference inphase of the torsional rigidity in the rotation direction from occurringbetween respective ones of a plurality of the gear devices.

(2) Preferably, the rotational phase adjusting means has a firstreference portion provided in the first cylindrical section at a givenposition offset from the axis thereof, a second reference portionprovided in the second cylindrical section at a given position offsetfrom the axis thereof, and a third reference portion provided in thecrankshaft or in a spur gear joined to the crankshaft, at a givenposition offset from the axis of the crankshaft.

According to this feature, in an operation of assembling the crankshaft,the crankshaft is assembled to allow the third reference portion to beset to a given position on the basis of the first reference portion andthe second reference portion, so that the crankshaft can be assembledsuch that an orientation thereof is set to a given state on the basis ofthe orientations of the first and second cylindrical sections about theaxis thereof.

(3) Each of the second and third reference portion may be formed as ahole.

According to this feature, during assembling of the crankshaft, atwo-forked or three-forked temporary locking pin is inserted to extendbetween the second reference portion and the third reference portioneach composed of a hole, so that it becomes possible to reliably set anorientation of the crankshaft with respect to the carrier. When thetemporary locking pin is subsequently detached, an eccentric oscillatinggear device can be provided in which the crankshaft is assembled to thefirst or second cylindrical section under a condition that theorientation of the crankshaft is adjusted to a given state.

(4) The crankshaft may be provided in a number of one. In this case, theone crankshaft may be disposed in concentric relation with respect tothe first or second cylindrical section.

(5) The crankshaft may be provided in a number of two or more. In thiscase, the two or more crankshafts may be disposed about the axis of thefirst or second cylindrical section at even intervals.

(6) One of the first and second cylindrical sections may be a carrier,and a remaining one of the first and second cylindrical sections may bean outer cylinder having internal teeth. In this case, the gear membermay be an externally toothed gear meshed with the internal teeth of theouter cylinder.

(7) One of the first and second cylindrical sections may be an outercylinder, and a remaining one of the first and second cylindricalsections may be a carrier having external teeth. In this case, the gearmember may be an internally toothed gear meshed with the external teethof the carrier.

As mentioned above, the eccentric oscillating gear device according tothe above embodiment is capable of reducing a variation in torsionalrigidity in a rotation direction.

What is claimed is:
 1. An eccentric oscillating gear device fortransmitting driving force while changing a rotation speed at a givenrotation speed ratio between a first member and a second member,comprising: a crankshaft having an eccentric portion; a gear memberhaving a tooth portion and a through-hole in which the eccentric portionis inserted; a first cylindrical section adapted to be attachable to oneof the first and second members; and a second cylindrical sectionadapted to be attachable to a remaining one of the first and secondmembers, wherein: one of the first and second cylindrical sectionsrotatably supports the crankshaft; a remaining one of the first andsecond cylindrical sections has a tooth portion meshed with the toothportion of the gear member; the first and second cylindrical sectionsare adapted to be rotatable concentrically and relatively with respectto each other according to an oscillating movement of the gear memberalong with a rotation of the crankshaft, and wherein the eccentricoscillating gear device is provided with a rotational phase adjustingsection for setting an orientation of the crankshaft about an axis ofthe crankshaft on the basis of orientations of the first and secondcylindrical sections about an axis of the first and second cylindricalsections so as to prevent the orientation of the crankshaft about theaxis of the crankshaft with respect to circumferential directions of thefirst and second cylindrical sections from changing from an orientationof the crankshaft before disassembling way when the crankshaft isre-assembled in the eccentric oscillating gear device.
 2. The eccentricoscillating gear device as defined in claim 1, wherein the rotationalphase adjusting section has a first reference portion, representing areference point of the first cylindrical section, provided in the firstcylindrical section at a given position offset from the axis thereof, asecond reference portion, representing a reference point of the secondcylindrical section, provided in the second cylindrical section at agiven position offset from the axis thereof, and a third referenceportion, representing a reference point of the crankshaft, provided inthe crankshaft or in a spur gear joined to the crankshaft, at a givenposition offset from the axis of the crankshaft.
 3. The eccentricoscillating gear device as defined in claim 2, wherein each of thesecond and third reference portion is formed as a hole.
 4. The eccentricoscillating gear device as defined in claim 1, wherein the crankshaft isthe only crankshaft provided in the oscillating gear device and isdisposed in concentric relation with respect to the first or secondcylindrical section.
 5. The eccentric oscillating gear device as definedin claim 1, wherein the crankshaft is provided in a number of two ormore, and wherein the two or more crankshafts are disposed about theaxis of the first or second cylindrical section at even intervals. 6.The eccentric oscillating gear device as defined in claim 1, wherein:one of the first and second cylindrical sections is a carrier; aremaining one of the first and second cylindrical sections is an outercylinder having internal teeth; and the gear member is an externallytoothed gear meshed with the internal teeth of the outer cylinder. 7.The eccentric oscillating gear device as defined in claim 1, wherein:one of the first and second cylindrical sections is an outer cylinder; aremaining one of the first and second cylindrical sections is a carrierhaving external teeth; and the gear member is an internally toothed gearmeshed with the external teeth of the carrier.
 8. A method of assemblinga crankshaft in an eccentric oscillating gear device for transmittingdriving force while changing a rotation speed at a given rotation speedratio between a first member and a second member, comprising the stepsof: assembling a crankshaft having an eccentric portion to a gearmember; assembling the crankshaft to one of a first cylindrical sectionand a second cylindrical section; assembling the gear member to aremaining one of the first and second members which has a tooth portion;and combining the first and second cylindrical sections together,wherein: the step of assembling the crankshaft to one of the firstcylindrical section and the second cylindrical section includes usingrotational phase adjusting section to set an orientation of thecrankshaft about an axis of the crankshaft with respect to one of thefirst and second cylindrical sections so as to prevent the orientationof the crankshaft about the axis of the crankshaft with respect to acircumferential direction of the one first and second cylindricalsections from changing from an orientation of the crankshaft beforedisassembling; and the step of combining the first and secondcylindrical sections together includes using the rotational phaseadjusting section to set an orientation of the second cylindricalsection about an axis of the second cylindrical section with respect tothe first cylindrical section.
 9. An eccentric oscillating gear devicefor transmitting driving force while changing a rotation speed at agiven rotation speed ratio between a first member and a second member,comprising: a crankshaft having an eccentric portion; a gear memberhaving a tooth portion and a through-hole in which the eccentric portionis inserted; a first cylindrical section adapted to be attachable to oneof the first and second members; and a second cylindrical sectionadapted to be attachable to a remaining one of the first and secondmembers, wherein: one of the first and second cylindrical sectionsrotatably supports the crankshaft; a remaining one of the first andsecond cylindrical sections has a tooth portion meshed with the toothportion of the gear member; the first and second cylindrical sectionsare adapted to be rotatable concentrically and relatively with respectto each other according to an oscillating movement of the gear memberalong with a rotation of the crankshaft, and wherein the eccentricoscillating gear device is provided with a rotational phase adjustingsection for setting an orientation of the crankshaft about an axis ofthe crankshaft on the basis of orientations of the first and secondcylindrical sections about an axis of the first and second cylindricalsections so as to prevent a difference of the orientation of thecrankshaft about the axis of the crankshaft with respect tocircumferential directions of the first and second cylindrical sectionsbetween respective ones of a plurality of eccentric oscillating geardevices from occurring when the crankshaft is assembled in the eccentricoscillating gear device.